My favorite feature of 3270/5250-style keyboard layouts is the separate carriage return and Enter keys, allowing for multiline text entry without special handling to avoid conflicts with the command to signify that input is complete.

With only a single combined Enter/Return key, it's hard to remember in any given context whether Shift+Enter or Control+Enter will open up a new line instead of immediately sending a message, dismissing a dialog box, completing input into a particular spreadsheet cell, editable filename, text object in a drawing program, etc., or whether I need to copy/paste a line break from another application because no such shortcut exists at all.